Flood warning technology needed

Prolonged heavy rains, poor flood drainage and limited flood forecasting have left people unable to react. Experts have proposed establishing a hydrological agency by basin, applying AI and re-planning flood drainage space.

Houses of people at the foot of Da Nhim dam ( Lam Dong ) were heavily flooded after Da Nhim hydroelectric reservoir discharged floodwater with a flow rate of more than 2,500m³/s in the middle of the night of November 19 - Photo: MV

Speaking with Tuoi Tre, Prof. Dr. Nguyen Quoc Dung, Vice President in charge of the Vietnam Association of Large Dams and Water Resources Development, assessed that the cause of the historic flooding in the South Central provinces was due to heavy rains, long-term rains, hydroelectric reservoirs that could not be controlled and were forced to release floodwaters.

Along with that, the flood-draining plain area has poor drainage, few river mouths, and the river mouths are filled up so floodwater cannot drain in time, leading to rapid flood rise. More synchronous solutions are needed to minimize flood damage when natural disasters become increasingly severe.

Mr. Dung assessed that during this flood, the local authorities have promptly intervened in reservoir operations and the reservoir owners have strictly complied. However, after this flood, there are still problems that need to be solved to improve the reservoir operation capacity, contributing to reducing flooding and affecting downstream areas.

We cannot keep blaming natural disasters and hydropower dams for flooding. Localities need to calculate and plan for flood drainage space downstream to ensure sustainable development. At the same time, it is necessary to integrate planning for traffic, irrigation, and drainage to avoid flooding.

Prof. Dr. Nguyen Quoc Dung

Firstly, our forecasting work is based on the National Center for Hydro-Meteorological Forecasting and this agency is forecasting over a large area, not specifically over a small area or river basin.

According to foreign experience, each river basin needs a hydrological calculation agency to advise the competent person (provincial chairman) to make decisions on reservoir operation. For example, in Japan, there are 11 large river basins, each basin has a hydrological office to do forecasting work to support the decision-making on operation. Meanwhile, in our country, the provincial chairman does not have an advisory agency to make early operation decisions in situations where extreme rain and floods are likely to occur.

According to Decree 62 on the guidance of the Electricity Law, the responsibility for consulting on the operation of hydroelectric reservoirs lies with the industry and trade sector. However, the industry and trade sector does not have people working in the field of hydrology and irrigation, so there is no timely consultation, even in cases where a notice is received but a decision on when to release water is not made.

"Therefore, institutionally, it is necessary to amend the direction so that each river basin must have a hydrometeorological agency with consulting duties and this task needs to be socialized to support competent authorities in making operational decisions," said Mr. Dung.

Second, applying science and technology to rain forecasting and reservoir operations. To have accurate rain forecasts, it is necessary to apply artificial intelligence combined with placing rain gauge stations in river basins to accurately forecast rain. From this forecast, run standardized hydrological and hydraulic models to calculate how much water will flow to the reservoir, how to operate it, and then make calculations to balance the benefits between the owner of the hydropower reservoir and the damage caused if the flood is released.

Mr. Dung further analyzed that in order for hydroelectric reservoirs in the Central region to proactively discharge floodwaters early before each heavy rain, it is necessary to study policies on purchasing flood prevention capacity to balance interests. In case the flood season ends and the hydroelectric reservoir is not full, the locality will compensate the reservoir owner with the natural disaster prevention fund.

Third, it is necessary to build a real-time flood map of the area on the website or app. For example, predict where the flood will rise in a few hours so that local authorities and people can be proactive and know which areas need to be evacuated first. "Currently, there are many situations where flood water comes in the middle of the night, and when people wake up, they see the water up to the roof. Therefore, it is necessary to improve flood forecasting and warning using science and technology, using calculation techniques to give warnings about which areas need to be evacuated first and which areas need to be evacuated later," Mr. Dung emphasized.

Coordination of hydroelectric reservoirs, irrigation and technology

At the forum on digital transformation, technology application in the operation and safety assurance of dams and reservoirs organized by the Department of Irrigation Works Management and Construction in collaboration with the Agriculture and Environment newspaper on November 21, Mr. Nguyen Tung Phong - Director of the Department of Irrigation Works Management and Construction ( Ministry of Agriculture and Environment ) - said that the recent heavy rains and floods have revealed many issues that need to be re-evaluated in both forecasting and inter-reservoir operation organization.

Regarding the upcoming orientation, Mr. Phong said that the irrigation industry must update the rain-flood database, design parameters and dam safety standards to match the new extreme weather values. Digital transformation does not stop at digitizing data but must help the industry solve practical problems such as flood forecasting, calculating flood storage capacity and supporting real-time decision making.

"Close coordination between irrigation and hydropower reservoirs, combined with the application of new technology and modern data, will be the foundation to ensure downstream safety and serve socio-economic development in the context of increasingly extreme climate," Mr. Phong added.

When releasing floodwaters, hydropower contributes 20-30%

Regarding the conflicting opinions about hydroelectric dams releasing floodwaters causing more serious flooding in the South Central provinces, especially the Ba Ha River hydroelectric dam, Mr. Dung said that hydroelectric reservoirs in the Central region are characterized by being located on the eastern slopes of the Truong Son mountain range, with high slopes and the downstream is often a very narrow plain.

For example, the Cai River Delta is only 200-300km² but the upstream water catchment area is up to 2,000km². Thus, the water catchment area is 10 times larger than the area spread over the delta, while a very large amount of rain in a short time is concentrated in this river basin, hydroelectric reservoirs in the South Central region can only reduce floods to a modest extent, so floods have to be concentrated in the delta.

"The opinions that flooding downstream is more serious due to hydroelectric reservoirs releasing floodwaters are generally about 20-30% correct because there are times when reservoirs release floodwaters when downstream areas are straining to fight floods, causing floods to rise quickly. This is a disadvantage in evacuating people, moving assets, and preventing natural disasters downstream. This is true, but we should not put all the blame on hydroelectric reservoirs releasing floodwaters," said Mr. Dung.

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Source: https://tuoitre.vn/can-canh-bao-ngap-lut-bang-cong-nghe-20251122082540704.htm